1. Field of the Invention
This invention relates to photographic apparatus, e.g., cameras, having a synchronized flash.
2. Description of the Prior Art
The prior art is replete with cameras having synchronized flash systems. In some cameras, e.g., see U.S. Pat. No. 3,634,725, the intensity of the light emitted by the flash is a function of the camera-to-subject distance. In other cameras, e.g., see U.S. Pat. No. 3,646,865, the duration of the flash is a function of the camera-to-subject distance. Still others terminate the flash in accordance with the amount of light received from the illuminated object. See U.S. Pat. No. 3,714,443. However, none of the above systems provides a means whereby the output of the ranging system is correlated with the movement of an objective lens assembly so as to provide a fire signal to the flash at the moment that the objective lens assembly is moving through a zone in which the subject to be photographed is in focus. To the contrary, the above cameras appear to have manually operative focusing systems wherein the objective lens assembly is stopped prior to operation of the flash system, when the objective lens assembly is at the precise location whereat the subject is properly focused at the camera's focal plane. This requires precise machining of the threads on the lens barrel, precise range markings on the lens bezel, etc., which adversely affect the cost of the camera.
U.S. Pat. Nos. 4,188,103 and 4,167,316 disclose systems wherein automatic sonic ranging systems produce an output which is continuously compared to a signal which is indicative of the location of an objective lens assembly for providing a fire signal to the flash at the appropriate moment. However, in each system, the objective lens assembly is stopped prior to the firing of the flash. Thus, each system requires an expensive dynamic braking apparatus for stopping the objective lens assembly at the precise location that the subject is in focus.
German Pat. No. 2,943,388 discloses a camera having an automatic focusing system including an automatic ranging system, a lens position sensing device, and a shutter control device which responds both to signals from the automatic ranging system and from the lens position sensing device to control the release of a shutter as the lens passes through a zone in which the subject being photographed is in focus. However, this system is silent as regard synchronized flash systems.